Herbert Spencer Gasser Biography (1888-1963)

neurophysiologist, physician

Herbert Gasser was born in Platteville, Wisconsin, on July 5, 1888. His mother, Jane Griswold, who descended from an early Connecticut family, was a teacher trained in Wisconsin's first State Normal School in Platteville. Gasser'sfather, Herman, was born in the Tyrol and came to the United States as a boy.Herman was a self-educated man who eventually qualified in medicine and became a country doctor.

After attending State Normal School, Gasser received two degrees in science at the University of Wisconsin, a bachelor's degree in zoology in 1910 and a master's in anatomy in 1911. However, Gasser's future interests were determined by a physiology course in the University's newly organized medical school.The young lecturer who emphasized the new spirit of research in medicine wasJoseph Erlanger, the man with whom Gasser would share the Nobel Prize 33 years later. In 1915, he earned his medical degree from Johns Hopkins University,where he conducted research on blood coagulation in his spare time. After another year of research in Wisconsin, Gasser joined Erlanger at Washington University in St. Louis, in 1916.

Earlier scientists had provided painstaking microscopic slides of neurons andgeneral theories of nerve networks in the body. Gasser's contributions madeit possible to trace pathways while keeping the nervous system intact. Physiologists knew that impulses (action potentials) travel along nerves to conveysensation and to stimulate muscles, and that these impulses could be recordedby electrical instruments. A hypothesis existed that impulses moved faster along thick fibers than they did thin ones. Gasser's dramatic new method involved stimulating a given region of nerves and then reading the transmitted signal as it reached its destination, much like a physician tests a patient's knee jerk response with a rubber mallet. His problem was in finding recording devices capable of measuring, in fractions of a second, impulses that were small in quantity and short in duration. The available devices were inadequate.The string galvanometer and the capillary electrometer were slow and insensitive. The cathode-ray oscillograph, although quick, was insensitive to small currents.

The first breakthrough for Gasser came with the same vacuum tube amplifier that made radio possible. The three-stage amplifier had been brought to St. Louis by H. Sidney Newcomer, one of Gasser's classmates at Hopkins, who had built the device with the help of friends at the Western Electric Company. Nerveimpulses could now be recorded, though the instrument's inertia caused distortions in timing the impulses. Their report describing this apparatus and experiments on nerves in the diaphragm appeared in 1921. This article was less important for its new knowledge about nerves than for its description of how sensations could at last be signalized.

A new technology, again from Western Electric, allowed Gasser and Joseph Erlanger to conduct the pioneering studies that eventually led to their Nobel Prize. It had been believed for over a decade that, should a means be discoveredto test the Braun tube, the nerve impulse might accurately be recorded. Butthe tube, invented in 1897, used a cold-cathode technology, wherein the emission of electrons from the cathode's electrode is triggered by an outside force--this proved to be its downfall. Western Electric had, on the other hand, developed an oscillograph tube fitted with a hot cathode. This permitted the instrument to operate at a low voltage, which made it more sensitive to the small currents of the nerve action potentials. The instrument could record boththe time elapsed between impulses and the change in nerve reactions. Thoughthe tube was a breakthrough for Gasser and Erlanger, they still had to deviseauxiliary apparatus to coordinate their induction shocks with the action potentials that were displayed on the screen. This work was reported in 1922.

Using the cathode-ray oscilloscope, Gasser and Erlanger almost immediately made two discoveries about the unexpected complexity they found in nerve trunks. In one, they determined that the sequence of events of nerve impulse transmission consists of two parts. There is an initial, large, rapid deviation inelectric potential, called the spike, which ascends then descends during theactual transmission. The spike is followed by a sequence of small, slow potential changes, called the after-potential, that first has a negative and thena positive deviation.

In their other discovery, Gasser and Erlanger found that the composite actionpotential of a nerve has a range of velocities. They eventually identified three distinct patterns based on the length of spikes and their after potentials, and classified the fibers into three main groups. The fastest and thickest are A fibers, the intermediate size are B fibers, while the thinnest and slowest are C fibers. Their findings thus confirmed the hypothesis that thick fibers conduct impulses faster than thin ones.

Erlanger and Gasser next showed how these three types of fibers are distributed over the incoming and outgoing fibers of the spinal cord, the sensory andmotor roots. The perception of pain is carried by the thin, slow fibers, while muscle sense and touch and muscle movement are conducted by the fastfibers. Gasser subsequently explored the excitability of nerve fibers in relation to after-potentials. He also continued to refine the oscilloscope, first using x-ray film and eventually a camera to record the impulses.

Gasser served as professor of pharmacology at Washington University from 1921to 1931. During a two-year leave of absence between 1923 and 1925, he workedwith Archibald V. Hill and Henry Hallett Dale in London, Walter Straub in Munich, and Louis Lapicque at the Sorbonne, on investigations involving muscle contractions and excitation of nerves. In 1931, Gasser became professor of physiology at Cornell University Medical College in New York City. In 1935, at age 47, Gasser became the second scientific director of the Rockefeller Institute for Medical Research, succeeding Simon Flexner. Gasser's medical training and his grasp of mathematical and physical sciences equippedhim well to lead and to comprehend the expanding field of scientific medicine. His tenure bridged the economic depression of the 1930s, World War II, andthe unsettling changes in the funding of scientific research after the war. Despite these trying times, Gasser, nevertheless, led the institute's transition from its original emphasis on pathology and infectious diseases to a broader biological approach to human diseases. From 1936 to 1957, he also served as editor of The Journal of Experimental Medicine.

During World War II, many Rockefeller Institute laboratories closed and theirfacilities and staff were organized to support war efforts. Gasser returnedto work he had done on chemical warfare during the first world war, chairinga civilian committee on research development in that field. So it was a greatsurprise for Gasser when a cable arrived in 1944 from Stockholm, announcingthat he had won a Nobel prize. Gasser retired from the institute in 1953 andwas succeeded by Detlev W. Bronk. With a change to emeritus status came the opportunity for Gasser to return to the laboratory. Instead of plunging into new areas of nerve physiology, he returned to unfinished work on differentiation of the thin C fibers. The introduction of electron microscopy helped him confirm many of his earlier findings. Gasser's scientific contributions were recognized by honorary degrees from twelve universities. He was elected to theNational Academy of Sciences in 1934, the American Philosophical Society in1937, and was a member of more than twenty other scientific societies in theUnited States, Europe, and South America. He received the Kober Medal in 1954, from the American Association of Physicians.

Following a second stroke, Gasser died in New York Hospital on May 11, 1963.

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